We are using the chemostat for studying the effect of changes in growth condition on the surface components and extracellular products particularly lipoteichoic acid of cariogenic bacteria; changes being followed by chemical, serological and microscopic procedures. The organisms chosen are representative strains of streptococci, lactobacilli and actinomycetes, with studies initially concentrating on those strains whose cell wall - carbohydrates - polysaccharides or teichoic acids - have been sufficiently characterized. These surface components are of importance in a) the identification of a particular organism and b) defining the nature of the organism's interaction with the environment. Lipoteichoic acid is a recognized component of the membrane of most gram-positive bacteria but it may also occur extracellularly in significant amounts. The bacterial cell surface is particularly sensitive to changes in growth conditions. Thus, by obtaining a clearer understanding of the effect of environmental conditions on the growth of cariogenic bacteria, we can better understand their role in inducing caries.